On Jan 6, 2009, at 4:03 PM, Colin Nielsen wrote:
One fairly serious problem is that the backlinked paths are
discontinuous,
with lots of gaps; the non-backlinked paths are continuous without
gaps.
I assume you used the "knight's move" option? I agree the
discontinuous paths may cause some problems, especially when trying to
vectorize the paths. However, the gaps are legitimate in the sense
that they were created by the knight's move which makes small jumps
for the sake of more accurate directionality (you can see this if you
look closely at drain_backlinkvsnobacklink.png). Unlike the old
r.drain function, the updated r.drain only draws the cells actually
used in the cost algorithm.
I'm not sure how we can overcome the vectorization problem though,
especially since you need vectorization to determine the overall
distance traveled.
I've posted screenshots of the tests at:
http://www.public.asu.edu/~cmbarton/files/grass_cost/
Thanks for the tests and the screenshots.
-Colin
Hi Colin,
Thanks for the updates. I'll give them a try. While I understand the
reason for the gaps in the paths now, I think that it is important to
find some way to get rid of them. That is, there needs to be some
algorithm that will 'connect the dots' of knights move jumps. These
are supposed to be paths traversing a landscape. Even without
vectorizing, the cell accumulation values will be inaccurate if cells
are skipped in a path from point A to point B.
Michael
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